Abstract Objectives: Delirium is a neuropsychiatric syndrome frequently observed in the elderly population (Korevaar, van Munster & de Rooij, 2005). The aim of this study was to determine if patients with delirium show measurable deficits in attentional functioning in comparison to a cognitively-impaired and cognitively-unimpaired group Subjects and Methods: A battery of tests that measured general cognitive functioning and attentional processing were administered to 20 delirium, 18 Alzheimer’s dementia and 19 cognitivelyunimpaired patients over the age of 65 Results: Using non-parametric measures it was shown delirium participants significantly differed from dementia and cognitively-unimpaired controls in all attentional tasks Conclusions: It is concluded attentional deficits are a key feature of delirium and in future could form the basis of a neuropsychological marker of this syndrome.